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Cardio Week 1 > Alpha Blockers > Flashcards

Alpha Blockers Flashcards

1
Q

What do alpha receptors do?

A

receptors in the vasculature that activate smooth muscle, thereby producing vasoconstriction both in skeletal muscle and in skin and splanchnic vessels.

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2
Q

What are some alpha blockers that have a much higher specificity for a1 than a2?

A
  • Doxazosin
  • Terazosin
  • Prazosin
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3
Q

What are some alpha blockers that have relatively equal specificity for a1 and a2?

A
  • Phenoxybenzamine (slightly more from a1)

- Phentolamine (equal)

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4
Q

What is yohimbine?

A

an alpha-2 antagonist used in treatment of erectile dysfunction

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5
Q

What are the types of alpha-1 receptors?

A

a, b, and d

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6
Q

What are alpha-1 receptors involved in?

A

smooth muscle contraction

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7
Q

Where are the subtypes of alpha-1 receptors located in the body?

A

b and d- vasculature

a- prostate mostly

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8
Q

Blockade of alpha-1a receptors in the bladder neck and prostate can do what?

A

improve urine flow rate and reduce symptoms of benign prostatic hypertrophy (BPH)

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9
Q

What is Alfuzosin?

A

more specific drug for alpha-1a receptors than other alpha-1 antagonists used for BPH

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10
Q

Where are alpha-1 and alpha-2 receptors located in relation to muscular junctions?

A

alpha-1 receptor on the post-synaptic
membrane where it mediates downstream events, and the alpha-2 receptor on the
presynaptic terminal, where it functions as an auto-receptor to terminate further
release of endogenous NE

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11
Q

What do alpha-1 receptors do?

A

activation of the receptor decreases production go cAMP leading to an inhibition of further release of norepinephrine from the neuron

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12
Q

What do alpha-2 receptors do?

A

activation of the receptor increases production go DAG and IP3, leading to an increase of intracellular calcium

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13
Q

Side effects of alpa-2 stimulation?

A
  • bradycardia and hypotension (due to stimulation of vagal activity.)
  • sedation
  • analgesia
  • reduced anesthetic requirements
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14
Q

What does block of alpha-1 receptors result in?

A

leads to hypotension, by preventing NE-stimulated

smooth muscle contraction in the vasculature.

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15
Q

Norepinephrine is an agonist for which receptors?

A

a1, a2, B1

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16
Q

Epinephrine is an agonist for which receptors?

A

a1, a2, B1, B2

17
Q

Isoproterenol is an agonist for which receptors?

A

B1, B2

18
Q

What does Isoproterenol do to BP?

A

decreases via beta receptor stimulation

19
Q

What do Norepinephrine and Epinephrine do to BP?

A

increases via primarily alpha receptor stimulation

20
Q

What would pre-treatment someone with an a-blocker and giving epi result in?

A

the a-blockers would block the alpha receptors so the major effect would be a decrease in BP even though if given alone the epinephrine would raise BP

this is called epinephrine reversal

21
Q

How would the a-blocker/epi combo affect CV?

A 
- increase in HR and renal blood flow            - `decrease in total
peripheral resistance (TPR), BP and effective refractory period (ERP) in the heart
22
Q

What would pre-treatment someone with a nonspecific b-blocker and giving epi result in?

A

Blocking the b-receptors would leave only a receptors and that would manifest in a spike in BP and there would be no CV effects upon the heart

23
Q

What are the side effects of alpha-blockers?

A
  • first dose orthostatic hypotension (most common in prazosin)
  • sinus tach (angina, palpitations)
  • syncope
  • vertigo
24
Q

T or F. Non-specific alpha-blockers like phentolamine are more likely than the alpha- 1 selective agents to produce tachycardia.

A

T, by virtue of the action augmenting the release of endogenous NE

25
Q

What does NE cause?

A

Although one thinks of NE as acting predominantly on
alpha-adrenergic receptors to produce constriction of resistance and capacitance
vessels, NE also acts on beta1-receptors, although quantitatively less than either
epinephrine or isoproterenol. In relatively lower doses, the cardiac-stimulant effect of norepinephrine is predominant; with larger doses, the vasoconstrictor effect
predominates.

26
Q

How does Phenoxybenzamine work?

A

it is a non-specific (1 and 2) alpha blocker that binds covalently (LONG LASTING) to both receptors where it produces a reduction of BP via vasodilation that is less intense than for alpha-1 specific blockers

27
Q

Why are the vaso-dilatative effects of non-specific alpha blockers less intense than specific ones?

A

because of the mitigating action of increased CO.

28
Q

What is Phenoxybenzamine approved to treat?

A

pheochromocytoma, a rare adrenal gland
tumor that produces excessive circulating levels of catecholamines and lifethreatening
sympathetic stimulation

29
Q

Off label uses of Phenoxybenzamine.

A

The drug is also used “off label” for conditions
involving poor perfusion of peripheral tissue like the fingers and toes- For example,
Raynaud’s syndrome, which is a condition found predominantly in women who have
vasospasm of the smaller arteries that supply blood to the skin, fingers and toes.

30
Q

Is Phenoxybenzamine fast acting?

A

No, slow onset but long lasting

31
Q

What else does Phenoxybenzamine do?

A

minor action of blocking serotonin, histamine, and acetylcholine

32
Q

What does the minor blocking of serotonin, histamine, and acetylcholine result in?

A
  • sinus tach, nasal congestion
  • drowsiness, fatigue, weakness, headache
  • ejaculation dysfunction
33
Q

What is Phentolamine?

A

a short acting non-specific alpha blocker

34
Q

What is Phentolamine used for?

A

hypertensive emergency and Pheochromocytoma

not for regular HTN

35
Q

What are the side effects of Phentolamine?

A

antagonizing alpha-2 receptors increases circulating nor due to loss of negative feedback

36
Q

What are the effects of small doses of Phentolamine?

A

positive inotropic effect dominates and BP increases via increased nor levels

37
Q

What are the effects of large doses of Phentolamine?

A

peripheral vasodilation predominates and BP decreases

38
Q

What happens if BP drops too low?

A

If BP falls too precipitously, the baroreceptors initiate sympathetic stimulation of the heart, leading to tachycardia

Cardio Week 1 (22 decks)

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